Indirect evidence suggests that there may be an efferent neural pathway in the auditory system which is involved in gating incoming stimuli during selective attention. The proposed study is an attempt to demonstrate the effects of selective attention on the early components of the auditory evoked potential (AEP). The few existing studies in this area with human subjects have failed to find such results. A number of methodological changes from these studies will be effected in order to optimize the chances of detecting such effects. First, a sufficiently large group of subjects (25) will be used. Instead of the typical binaural listening task, which has not shown any attention-related effects on AEP components prior to N1 (100 msec. post stimulus), an auditory detection task will be compared to a visual task (a paradigm similar to one in which early attention-related gating effects have been demonstrated in animals). Finally, an increase in resolution of the brain stem auditory evoked potential (BAEP) will make it possible to detect any small but consistent attention-related changes in these early components of the AEP.